Kinetics of radical-ion pairs (RIPs) formed by photoinduced electron transfer in solution, as well as triplet and singlet products of their recombination, are studied within a general theory of spin-selective charge transfer assisted by diffusion of reactants in solution. The RIPs are assumed to be created in the singlet state, and their coherent singlet–triplet evolution is described in terms of isotropic hyperfine interaction (HFI) and \(\Delta g\) mechanisms. A set of quantum-classical model equations is solved numerically using the time propagator splitting technique. Numerical simulations are carried out on a prototype photochemical reaction involving bimolecular electron transfer between 9,10-dimethylanthracene (DMeA) and phthalonitrile (PN) in acetonitrile (ACN) solution. Time-dependent populations of all electronic and spin states, as well as spatial distributions of reactants in the course of forward and backward charge transfer are calculated and analysed. Particularly, spatial profiles of charge recombination (CR) in singlet and triplet RIPs are shown to differ significantly, with a significant part of the singlet RIPs undergoing distant (non-contact) recombination. The effect of a strong (saturating) magnetic field on the triplet CR product yield in these reactions is studied. For the HFI-induced coherent spin transitions, the time-dependent magnetic field effect is shown to decrease with time. A phenomenon of suppressing the triplet CR product yield in RIPs with the HFI- and \(\Delta g\)-induced coherent spin transitions in moderate magnetic fields is investigated and its physical origins are discussed.

在溶液中反应物扩散辅助的自旋选择性电荷转移的一般理论中，研究了溶液中光致电子转移形成的自由基离子对 (RIP) 的动力学，以及它们复合的三线态和单线态产物。假设 RIP 是在单线态下产生的，并且它们的相干单线-三线态演化用各向同性超精细相互作用 (HFI) 和\(\Delta g\) 来描述机制。使用时间传播子分裂技术对一组量子经典模型方程进行数值求解。对涉及 9,10-二甲基蒽 (DMeA) 和邻苯二甲腈 (PN) 在乙腈 (ACN) 溶液中的双分子电子转移的原型光化学反应进行了数值模拟。计算和分析了所有电子和自旋态的时间相关种群，以及正向和反向电荷转移过程中反应物的空间分布。特别是，单线态和三线态 RIP 中电荷复合 (CR) 的空间分布显示出显着不同，其中很大一部分单线态 RIP 经历了远距离（非接触）重组。研究了强（饱和）磁场对这些反应中三线态 CR 产物产率的影响。对于 HFI 诱导的相干自旋跃迁，随时间变化的磁场效应会随着时间的推移而降低。抑制 RIP 中三线态 CR 产物产率的现象与 HFI-和研究了\(\Delta g\) -在中等磁场中引起的相干自旋跃迁，并讨论了其物理起源。